he was the deadliest sniper in u.s. military history. >> i loved the job, the guys, the camaraderie. it came down to where i had to choose them or my wife and kids. i couldn't have both any more because i'd already messed that up. so i chose the family. >> reporter: on the home front kyle became a best selling author. in his autobiography "american sniper" he writes of shooting so many iraqi insurgents they nicknamed him the devil. to survive all of that to be killed only here at home. tonight that young marine faces two counts of capital murder, one for each of the men who was trying to help him heal. >>> navy s.e.a.l. chris kyle often said himself how difficult it was for troops to return from war. from serving the greater good, he said, overseas, to serving their own good once home. and this number tonight, nearly 20% of returning troops suffer from symptoms of post-traumatic stress. and they're the ones we know about. martha raddatz in the middle east tonight reporting on what might be an invisible epidemic. >> repo